Associations between renal impairment and anemia in older, rural Japanese men: the Nagasaki Island study
© Shimizu et al.; licensee BioMed Central Ltd. 2014
Received: 13 December 2013
Accepted: 2 April 2014
Published: 17 April 2014
Renal impairment is known to be associated with atherosclerosis, which in turn is reported to be positively associated with hemoglobin levels. In addition, renal impairment is known to be associated with a form of anemia known as renal anemia.
To clarify the associations between renal impairment and anemia, we conducted a cross-sectional study of 1,105 60 to 89-year-old men, who were not taking medication for anemia and were undergoing general health check-ups.
Compared with non-chronic kidney disease, chronic kidney disease (CKD) with a glomerular filtration rate (GFR) <60 mL/min/1.73 m2 was found to constitute a significant risk of anemia. However, we noted that this risk was lower for mild renal impairment (60 mL/min/1.73 m2 ≤ GFR <90 mL/min/1.73 m2). Compared with the non-CKD reference group, the classical cardiovascular risk factors adjusted odds ratio (OR) for anemia was 1.81 (1.23 to 2.68) and compared with the normal renal function (GFR ≥90 mL/min/1.73 m2) reference group, the ORs for mild renal impairment and CKD were 0.26 (0.15 to 0.47) and 0.60 (0.33 to 1.09).
Independent from classical cardiovascular risk factors, CKD, which was identified during general health check-ups, appeared to constitute a significant risk of anemia for older Japanese men. For mild renal impairment, however, this association was a reduced risk of anemia and thus possibly a higher risk of atherosclerosis.
KeywordsGFR Anemia Renal impairments CKD Men
A decline in the glomerular filtration rate (GFR) was identified as a marker of chronic kidney disease (CKD) that is known to be associated with a form of anemia known as renal anemia.
In a previous study of ours, positive associations were detected between hemoglobin levels and increased arterial stiffness assessed with the cardio-ankle index (CAVI) . Since CAVI was identified as an independent factor associated with GFR in the general population , renal impairment might also be positively associated with hemoglobin levels.
To investigate this potential association, we conducted a cross-sectional study of older Japanese men who participated in a general health check-up between 2005 and 2012.
The survey population covered 1,175 men aged 60 to 89 years, who were all residents of the western Japan rural community of the Goto Islands and participated in this study between 2005 and 2012. We used data that were obtained the first time the subjects participated in this study. A total of 66 individuals with missing data and 4 individuals who were taking medication for anemia were excluded, leaving 1,105 men for enrollment in this study. The mean age of the study population was 70.2 years (±6.7 SD; range 60 to 89). Written consent forms were available in Japanese to ensure comprehensive understanding of the study objectives, and informed consent was signed by the participants. This study was approved by the Ethics Committee for Use of Humans of Nagasaki University (project registration number 0501120073).
Data collection and laboratory measurements
Systolic blood pressures were recorded at rest. Body weight and height were measured with an automatic body composition analyzer (BF-220; Tanita, Tokyo, Japan) at the same time blood was drawn. Trained interviewers obtained information on smoking status, drinking status, medical history, use of antihypertensive agents, and use of medication for diabetes mellitus. Fasting blood samples were obtained in an EDTA-2 K tube and were used for measuring hemoglobin with the sodium lauryl sulfate (SLS)-hemoglobin method. Serum concentrations of HDL cholesterol, triglycerides (TG), aspartate aminotransferase (AST), γ-glutamyltraspeptidase (γGTP), creatinine, and hemoglobin A1c (HbA1c), were measured with standard laboratory procedures. The glomerular filtration rate (GFR) was estimated by using an established method with three variations recently proposed by a working group of the Japanese Chronic Kidney Disease Initiative .
Definition of disease
Anemia for men was defined as 13 g/dL > hemoglobin in accordance with the recommendation by the World Health Organization (WHO) Study Group . Diabetes was defined as HbA1c ≥6.5% (NGSP: National Glycohemoglobin Standardization Program) and/or initiation of glucose-lowering medication or insulin therapy . On the basis of the Kidney Disease Outcomes Quality Initiative Clinical Practice Guidelines , we defined normal renal function as GFR ≥90 mL/min/1.73 m2, reduced renal function as GFR <90 mL/min/1.73 m2, mild renal impairment as GFR 60 to 89 mL/min/1.73 m2, and CKD as GFR <60 mL/min/1.73 m2.
Differences in age-adjusted mean values or prevalence of potential confounding factors in relation to hemoglobin levels were calculated using ANOVA or logistic regression models. Odds ratios (ORs) and 95% confidence intervals (CIs) for anemia associated with renal impairment (both mild renal impairment and CKD) were calculated with the aid of logistic regression models. First, we adjusted only for age. Second, we included other potential confounding factors, that is, smoking status (never a smoker, former smoker, current smoker), alcohol consumption (non-drinker and current light to moderate drinker (1 to 6 times/week), current heavy drinker (every day)), systolic blood pressure (mmHg), antihypertensive medication use (no, yes), body mass index (kg/m2), diabetes (no, yes), history of cardiovascular disease (no, yes), HDL cholesterol (mg/dL), TG (mg/dL), AST (IU/L), and γGTP (IU/L). All statistical analyses were performed with the SAS system for Windows (version 9.3; SAS Inc., Cary, NC, USA). All P values for statistical tests were two-tailed, and values of <0.05 were regarded as statistically significant.
Of the 1,105 men taking part in the general health check-up program, 645 were diagnosed with mild renal impairment and 351 with CKD, while 162 were diagnosed with anemia.
Age-adjusted mean values and percentage in relation to renal function
Non-chronic kidney diseased
Chronic kidney diseasec
Normal renal functiona
Mild renal impairmentb
Number at risk
67.7 ± 6.1
69.6 ± 6.5
72.2 ± 6.7
Systolic blood pressure, mmHg
Antihypertensive medication use, %
History of cardiovascular disease, %
Body mass index, kg/m2
Current drinkers, %
Current smokers, %
Serum HDL cholesterol, mg/dL
Serum triglycerides (TG), mg/dL
Serum aspartate aminotransferase (AST), IU/L
Serum γ-glutamyltraspeptidase (γGTP), IU/L
Serum creatinine, mg/dL
Glomerular filtration rate (GFR), mL/min/1.73 m2
Odds ratios (OR) and 95% confidence intervals (CI) for anemia in relation to glomerular filtration rate (GFR) levels
Non-chronic kidney diseased
Chronic kidney diseasec
Normal renal functiona
Mild renal impairmentb
Number at risk
Number of cases (percentage)
1.54 (1.08 to 2.20)
0.26 (0.16 to 0.45)
052 (0.30 to 0.89)
1.81 (1.23 to 2.68)
0.26 (0.15 to 0.47)
0.60 (0.33 to 1.09)
Participants with CKD and anemia showed significantly lower GFR whereas their non-CKD counterparts showed significantly higher GFR. The age-adjusted values for GFR were 50.6 mL/min/1.73 m2 for participants with non-anemic CKD and 44.8 mL/min/1.73 m2 for those with anemic CKD (P <0.001). For non-CKD participants, the corresponding values were 75.5 mL/min/1.73 m2 and 84.3 mL/min/1.73 m2 (P <0.001).
As part of our study, we conducted a further investigation of 1,059 men for whom CAVI data were available. We found that both GFR and hemoglobin were significantly associated with atherosclerosis (CAVI ≥9.0). The age-adjusted odds ratios for risk of atherosclerosis of a one standard deviation (SD) increment in GFR (17.3 mL/min/1.73 m2) and in hemoglobin (1.3 g/dL) were 0.82 (0.71 to 0.95, P = 0.007) and 1.31 (1.14 to 1.50, < 0.001), respectively.
The major finding of the study presented here was that CKD, which was diagnosed during general health check-ups, seems to represent a significant risk of anemia for older, rural Japanese men. Since this association was the result of the reduced risk of anemia for mild renal impairment, which might be associated with atherosclerosis, this finding may constitute an important tool for clinical practice dealing with renal impairment.
This study has certain potential limitations, which warrant consideration. One of these is that we could not establish any causal relationships because this study was cross-sectional. Since we consider the positive association between hemoglobin and renal impairment to be caused by active atherosclerosis progression, the atherosclerosis should also be classified into stable and progressive atherosclerosis. This indicates the need for a longitudinal study with a larger number of participants.
In conclusion, CKD appeared to constitute a significant risk of anemia for older, rural Japanese men as determined during general health check-ups. For mild renal impairment, however, this association was the result of a reduction in the risk of anemia and thus possibly a higher risk of atherosclerosis.
Chronic kidney disease
Glomerular filtration rate
National Glycohemoglobin Standardization Program
Sodium lauryl sulfate
World Health Organization
This work was supported by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (No. 22370090).
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